In a conventional front section, the width of the bumper cross member is considerably smaller than that of the bumper shell. If a central zone of the bumper shell strikes an external object and undergoes deformation as a result of such contact, this is detected reliably by the pressure sensor. In theory, however, peripheral zones of the bumper shell that are located beyond the ends of the bumper cross member, can be deformed to any degree, and this will not be detected by the shock sensor. Pedestrian protection measures that should be triggered in response to the signal from a shock sensor, are therefore not activated when only a peripheral zone of the bumper shell collides with the pedestrian and such a collision does not cause sufficient deformation of the central zone.
It might be feasible to adjust the width of the bumper cross member to the width of the bumper shell, but consequently this would mean that the edges of the bumper shell would have to satisfy the same requirements as the central zone with regard to a collision with a leg. For this, the front of the vehicle as far as the edges would have to be aligned essentially perpendicularly with the lengthwise direction of the vehicle; the rounding of bodywork corners, which is both aerodynamically favorable and helps to protect a pedestrian by guiding him to the side past the vehicle, is no longer possible.